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<html xmlns="http://www.w3.org/1999/xhtml">
 <head>
  <title>CSS Test: blur computation for box-shadow</title>
  <link rel="author" title="L. David Baron" href="http://dbaron.org/" />
  <link rel="author" title="Mozilla Corporation" href="http://mozilla.com/" />
  <link rel="help" href="http://www.w3.org/TR/css3-background/#the-box-shadow"/>
  <meta name="flags" content="" />
  <meta name="assert" content="the resulting shadow must approximate (with each pixel being within 5% of its expected value) the image that would be generated by applying to the shadow a Gaussian blur with a standard deviation equal to half the blur radius" />
  <style type="text/css">
    div.stripecontainer {
      width: 600px;
      height: 30px;
      border: medium solid blue;
    }
    div.refimage, div.blurcontainer {
      width: 600px;
      height: 10px;
    }
    div.refimage img {
      display: block;
    }
    div.blurcontainer { position: relative; overflow: hidden }
    div.blur {
      position: absolute;
      width: 2000px;
      height: 2010px;
      top: -1000px; /* places 1000px both above and below container */
      left: -2000px; /* places right edge at left of container */
      box-shadow: 300px 0 100px black;
    }
  </style>
 </head>
 <body>
  <p>The following test should contain three grayscale stripes, each 10
  pixels tall, with no space between them, but all enclosed within a
  blue border.  At all points, the middle stripe must be <strong>the
  same color as or darker than</strong> the top stripe, and <strong>the
  same color as or lighter than</strong> the bottom stripe.  (This tests
  that the blurring algorithm produces results within 5% of a Gaussian
  blur.)</p>
  <div class="stripecontainer">
   <div class="refimage"><img height="10" width="600" src="support/box-shadow-blur-definition-001-light-bound.png" alt="[reference stripe image]" /></div>
   <div class="blurcontainer"><div class="blur"></div></div>
   <div class="refimage"><img height="10" width="600" src="support/box-shadow-blur-definition-001-dark-bound.png" alt="[reference stripe image]" /></div>
  </div>
 </body>
</html>
